S. S. Malhi¹, M. Nyborg², E. D. Solberg³, B. McConkey⁴, M. Dyck², D. Puurveen² and D. Leach¹

¹Agriculture and Agri-Food Canada, Melfort, Saskatchewan, Canada (sukhdev.malhi@agr.gc.ca)

²Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada

³Alberta Agriculture, Food and Rural Development, Edmonton, Alberta, Canada

⁴Agriculture and Agri-Food Canada, Swift Current, Saskatchewan, Canada

Abstract

Field experiment (with mainly barley; canola, wheat, triticale, or pea in a few years) was conducted on a Gray Luvisol (Typic Cryoboralf) loam at Breton, Alberta, Canada, to determine the effects of 27 years (from 1983 to 2009 growing seasons) of straw management [straw removed and straw retained] and N fertilizer rate (0, 25, 50 and 75 kg N ha^-1) on soil biochemical [total organic C (TOC) and N (TON), light fraction organic C (LFOC) and N (LFON)], and chemical (pH, extractable P, ammonium-N and nitrate-N) properties under conventional tillage. Straw retention and N fertilizer treatments increased mass of TOC, TON, LFOC and LFON in soil, but the differences were more pronounced for LFOC and LFON. There were close and significant correlations among most soil organic C or N fractions. Linear regressions between crop residue C input and soil organic C or N were significant in most cases. Application of N fertilizer reduced pH and extractable P in the 0-15 cm soil layer. Residual nitrate-N (though quite low) increased with N rate and also indicated some downward movement in the soil profile up to 90 cm depth. There was generally no effect of any treatment on ammonium-N in soil. In conclusion, straw retention and N application improved organic C and N in soil, and differences were usually more pronounced for light fraction than total organic C and N, and between the most extreme treatments (S_Rem0 vs. S_Ret75). Application of N fertilizer reduced extractable P and pH in the surface soil, and showed some accumulation and downward leaching of nitrate-N in the soil profile.  

Mode of Presentation: Poster